Fatty acid alkyl esters may be used as fuel, biodiesel, in standard diesel engines. Biodiesel can be used alone, or blended with fossil diesel. Biodiesel has become more attractive recently because of its environmental benefits.
Although biodiesel is at present primarily produced chemically (using e.g., NaOH and/or sodium methoxide as catalyst), there are several associated problems to restrict its development, such as pre-processing of oil due to high contents of free fatty acids, need for high alcohol surplus in reaction removal of chemical catalyst from ester and glycerol phase, and removal of inorganic salts during glycerol recovery.
The disadvantages caused by chemical catalysts are largely prevented by using lipolytic enzymes as the catalysts and in recent years interest has developed in the use of lipases in transesterification for the production of biodiesel.
Biodiesel produced by enzymatic bioconversion is, compared with chemical conversion, more environmental friendly. However, with very few exceptions, enzyme technology is not currently used in commercial scale biodiesel production.
To make the production of biodiesel economically feasible, the enzyme cost must be as low as possible. This can only be achieved by re-use of the enzyme whether it is an immobilized or a liquid lipase formulation. To be able to use and reuse a liquid enzyme, the enzyme needs to be in the reactant mixture as part of a water phase.
Processes for enzymatic production of fatty acid alkyl esters using liquid enzymes are described in e.g., WO 2006/072256 and Lv et al. (Process Biochemistry 45 (2010) 446-450).